1. Field of the Invention
The present invention relates to an apparatus for drying a substrate. More particularly, the present invention relates to an apparatus for drying a substrate using an isopropyl alcohol vapor.
2. Description of the Related Art
Recently, the technology for manufacturing semiconductor devices has been improved in order to enhance integration density, reliability, response speed, and similar characteristics, thereby meeting various requirements of consumers. Generally, semiconductor devices are manufactured through a series of manufacturing processes for forming various films on a silicon wafer, which is used as semiconductor substrate, into patterns having electrical characteristics after the various films are formed on the semiconductor substrate.
The patterns are formed by repeatedly performing a series of unit manufacturing processes including a film deposition process, a photolithography process, an etching process, an ion implantation process, a polishing process and the like. During the processing, impurities such as reaction by-products and minute particles, remain on the semiconductor substrate. These impurities can cause fatal failures during subsequent manufacturing processes. Thus, a cleaning process and a drying process should be performed on the semiconductor substrate after the unit manufacturing processes. The cleaning process includes a wet cleaning process using various cleaning solutions and a dry cleaning process using a reactive gas. A rinsing process using de-ionized water and a drying process is performed after the cleaning process.
Typically, the drying process may be divided into two processes. First, there is a vapor drying process that removes a fluid (e.g., de-ionized water used in the rinsing process) and particles remaining on the surface of a semiconductor substrate by reducing a surface tension of the remaining fluid on the surface of the semiconductor substrate after an isopropyl alcohol vapor is condensed on the surface of the semiconductor substrate. Second, there is a Marangoni drying process that removes the remaining fluid and particles from the semiconductor substrate by passing the semiconductor substrate through an isopropyl alcohol layer formed on de-ionized water. An isopropyl alcohol vapor or mist is condensed not on the surface of the semiconductor substrate, but on the surface of de-ionized water to form the isopropyl alcohol layer.
FIG. 1 illustrates a schematic cross-sectional view of a conventional apparatus for drying a substrate. FIG. 2 illustrates a schematic side view showing the apparatus for drying a substrate as shown in FIG. 1.
Referring to FIGS. 1 and 2, a substrate drying apparatus 100 dries a plurality of semiconductor substrates W using an isopropyl alcohol vapor 10. In the apparatus, isopropyl alcohol 12 is received in a container 102, and a heater 104 is disposed beneath the container 102 to heat the isopropyl alcohol 12, thereby generating the isopropyl alcohol vapor 10.
An opening 102a is formed through an upper portion of the container 102 for loading and unloading the substrates W. A supporting member 110 for supporting the substrates W extends to the outside of the container 102 through the opening 102a. The supporting member 110 may include a plurality of holders 112 and a plurality of vertical arms 114 connected to the plurality of holders 112. The plurality of holders 112 support the substrates W in the vertical direction and side by side in the horizontal direction. The vertical arms 114 extend upwardly through the container 102 and out through the opening 102a. A plurality of slots (not shown) are formed in the holders 114, each of the slots supporting a corresponding one of the plurality of substrates W.
In operation, the substrates W are loaded into the container 102 through the opening 102a. The substrates W are dried at a position adjacent to the isopropyl alcohol 12 received in the container 102. A cooling coil 116 is disposed over the substrates W, which are supported by the supporting member 110, in order to condense the isopropyl alcohol vapor 10. The cooling coil 116 is installed along an inner sidewall of the container 102. The isopropyl alcohol vapor 10 in the container 102 is condensed via the cooling coil 116, and then the condensed isopropyl alcohol drops to a lower portion of the container 102.
The isopropyl alcohol vapor 10 generated by the heater 104 condenses on the surfaces of the substrates W, which have a relatively low temperature. At that time, a surface tension of the fluid on the surfaces of the substrates W weakens due to the condensed isopropyl alcohol so that the fluid flows down from the surfaces of the substrates W. The remaining impurities on the substrates W are removed from the substrates W by the flow of the fluid having the weakened surface tension.
A receiver tray 118 is installed under the substrates W, which are supported by the supporting member 110, to receive the fluid dripped from the substrates W. A draining pipe 120 is connected to the receiver tray 118 for draining the fluid from the receiver tray 118. The draining pipe 120 passes through a sidewall of the container 102 and extends to the outside. An isopropyl alcohol supplying pipe 122 is connected to an opposite sidewall of the container 102 to provide the isopropyl alcohol 12 into the container 102.
An air cleaner 160 for providing clean air is disposed over the container 102 to prevent minute particles from flowing into the container 102. The air cleaner 160 includes a high efficiency particulate air (HEPA) filter. In FIGS. 1 and 2, arrows indicate the flow of the clean air.
The inner space of the container 102 is divided into an isopropyl alcohol region 20 and a clean air region 22. Clean air flows into the clean air region 22 of the container 102 through the opening 102a. Reference numeral 30 indicates a boundary surface between the isopropyl alcohol region 20 and the clean air region 30.
In this conventional apparatus, a central portion of the isopropyl alcohol region 20 protrudes upwardly, as shown in FIGS. 1 and 2, because the cooling coil 116 is positioned along the inner sidewall of the container 102 and the clean air flows into the container 102 through the opening 102a. The density of the isopropyl alcohol vapor is low at a portion of the isopropyl alcohol region 20 adjacent to the cooling coil 116 since the portion of the isopropyl alcohol region 20 adjacent to the cooling coil 116 has a relatively low temperature as compared to the temperature of the central portion of the isopropyl alcohol region 20. The clean air flowing into the container 102 through the opening 102a is provided to a bottom portion of the container 102 through the portion of the isopropyl alcohol region 20 having the relatively low density. Hence, the peripheral portion of the container 102 has a density of the isopropyl alcohol vapor lower than that of the central portion of the container 102, thus causing an unstable flow of the isopropyl alcohol at the peripheral portion of the container 102 as compared to the central portion of the container 102. As a result, the isopropyl alcohol vapor 10 cannot be stably provided onto the surfaces of the substrates W positioned at the peripheral portion of the container 102 so that the substrates W positioned at the peripheral portion cannot be sufficiently dried.
More particularly, when the substrates W including patterns are positioned at the peripheral portion of the container 102, watermarks may be formed on the surfaces of the substrates W including the patterns. These watermarks decrease the reliability and the productivity of the semiconductor device. In addition, native oxide films may be formed on the surfaces of the substrates W as the surfaces of the substrates W come into contact with the clean air as the dried substrates W are unloaded from the container 102.